Search results
Results from the WOW.Com Content Network
Vitamin A deficiency is the leading cause of preventable childhood blindness worldwide and is a major cause of childhood mortality. [1] Each year, approximately 250,000 to 500,000 malnourished children in the developing world go blind from a VAD, with about half of whom dying within a year of losing their sight. [ 2 ]
Vitamin A status involves eye health via two separate functions. Retinal is an essential factor in rod cells and cone cells in the retina responding to light exposure by sending nerve signals to the brain. An early sign of vitamin A deficiency is night blindness. [6] Vitamin A in the form of retinoic acid is essential to normal epithelial cell ...
Keratomalacia is an eye disorder that results from vitamin A deficiency. Vitamin A is required to maintain specialized epithelia (such as in the cornea and conjunctiva ). The precise mechanism is still not known, but vitamin A is necessary for the maintenance of the specialized epithelial surfaces of the body.
No vitamin A toxicity has ever been reported from ingestion of excessive amounts. [24] Overconsumption of beta-carotene can only cause carotenosis, a harmless and reversible cosmetic condition in which the skin turns orange. Preformed vitamin A absorption and storage in the liver occur very efficiently until a pathologic condition develops. [21]
A major cause of Bitot's spots is vitamin A deficiency (VAD). [4] Rarely, pellagra due to deficiency of vitamin B 3 (niacin) may also cause Bitot's spots. [5] They can also be caused by Colestyramine , which is a bile acid sequestrant which can reduce the absorption of fat soluble vitamins (Vitamins A, D, E, K)
Entropion, severe dry eye and trichiasis (inturning of eyelashes) may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera . These include Rheumatoid arthritis, rosacea, systemic sclerosis which lead to a special type of corneal ulcer called Mooren's ulcer.
Vitamin A palmitate is a common vitamin supplement, available in both oral and injectable forms for treatment of vitamin A deficiency, under the brand names Aquasol A, Palmitate A and many others. It is a constituent of intra ocular treatment for dry eyes at a concentration of 138 μg/g (VitA-Pos) by Ursapharm.
Hypervitaminosis is a condition of abnormally high storage levels of vitamins, which can lead to various symptoms as over excitement, irritability, or even toxicity. Specific medical names of the different conditions are derived from the given vitamin involved: an excess of vitamin A, for example, is called hypervitaminosis A.